The present invention relates generally to processes and compositions for making molded articles that have improved properties. The molded articles are made for polymeric resinous materials, and are easily removed from a mold and preferably provide an improved surface for coating. More particularly, it relates to techniques and/or compositions involving the use of a reaction product of a glycoside and a fatty acid source to facilitate removal of molded resin products from molds and, preferably, to also provide an improved tie-coating surface to said molded resin products.
Resins based on various polymers are used in the production of molded objects. In general, such resins must be thermoplastic or thermosetting in order to perform satisfactorily. Examples of thermoplastic resins include polyamides, polyesters, polyurethanes, polypeptides, ether and acetal polymers, polysulfides, polycarbonates, polyolefins, polystyrenes, polyvinyl chlorides, acrylonitrile butadiene styrene resins, acrylic resins, and the like. Examples of thermosetting resins include phenolic resins, amino resins, unsaturated polyester resins, epoxy resins, cross-linked polyurethanes, silicone polymers and similar resins.
Resins based on organic polyisocyanates, as for example, polyurethane products, are well known and enjoy widespread commercial use in reaction injection molding (RIM) applications in which molded resin products are obtained through reaction of polyisocyanates with hydroxyl or amine containing molecules within a mold cavity. Polyurethanes constitute a broad class of polymeric materials having a wide range of physical characteristics. The polymers are produced through the interaction of a polyisocyanate with a chemical compound having two or more active hydrogen atoms in its structure such as a polyol, or polyether/polyester that contains active hydrogen groups in the form of amines, amides or hydroxyls, or mixtures of two or more of such materials. This component used in preparing the polyurethane is generally termed in the art as an "active-hydrogen-containing material" and is generally liquid, or a solid capable of being melted at a relatively low temperature. The materials most typically used contain hydroxyl groups as the radicals having the active hydrogen and thus are generally termed "polyols." The preparation of polyurethanes is disclosed, for example, in U.S. Pat. No. 2,888,409 issued May 26, 1959 and in the patents referred to therein. In addition, other hydroxyl-capped polymers useful as the polyol in preparing polyurethane resins include polyformals as described, for example, in U.S. Pat. No. 3,055,871 issued Sept. 25, 1982 to Heffler et al.; hydroxyl-terminated lactone polyesters described in U.S. Pat. No. 3,051,687 issued Aug. 28, 1962 to Young et al.; and alkylene oxide adducts of the allyl alcohol-styrene polymers described in U.S. Pat. No. 2,965,615 issued Dec. 20, 1960 to Tass, et al. It is conventional to use a polyol as a source of active hydrogen donor in the reaction, see for example, U.S. Pat. No. 3,383,351 issued May 14, 1968 to Stamberger.
Difficulties have occurred in the molding of the polyurethanes because of sticking of the polyurethanes to the molds in which they are produced. This sticking has, in the past, been overcome by the coating of the molds with an external mold-release agent, for example, see U.S. Pat. No. 3,178,490 issued Apr. 13, 1965 to Petrino, et al. However, such coating is expensive and time consuming during molding operations. Further, some of the external mold release agents leave a residue on the surface of the polyurethane which often interferes with the coating applied later.
British Pat. No. 1,365,215 issued Aug. 29, 1974 to Kleimann et al. discloses additives included in foamable reaction mixtures to impart mold parting properties. More particularly, this patent sets forth additives comprising salts of aliphatic carboxylic acids with primary amines, and an ester of a monofunctional and/or polyfunctional carboxylic acid, or a natural or synthetic oil, fat or wax.
The problem of polyurethanes sticking during molding is specifically recognized in U.S. Pat. No. 4,254,228 issued Mar. 3, 1981 to Kleimann et al., which discloses a reaction product of a fatty acid ester and polyisocyanate included in a foamable reaction mixture containing an organic polyisocyanate, polyol and blowing agent to provide a molded product which can be removed from a mold whose surfaces have not been coated with conventional external mold-release agents. However, this method is undesirably complex or complicated in that it involves the separate or initial formation of a preformed polyisocyanate/fatty acid intermediate reaction product and the subsequent addition of same to the main foamable polyisocyanate reaction mixture, for the formation of the polyurethane in the mold. Further, the pre-reaction of the fatty acid ester with the polyisocyanate reduces the amount of reaction in the molding process and limits migration of the ester resulting in less mold release agent available at the molded surface.
As is apparent from the foregoing, the general techniques or idea of including various sorts of additives in the reaction mixture is a known technique and, as above indicated, various additives, commonly known or referred to as "internal mold release agents", have been suggested and used. However, these additives, have generally either not provided acceptable mold release properties and/or have not provided suitable surface characteristics to the molded product for binding coatings to the polyurethane. The application of coatings such as paints, varnishes and the like to the molded products is a requirement in respect to many molded products. In the past, the mold release agents, especially in the case of external mold release agents, such as silicones, have adversely affected the ability to coat molded resin products. Thus, it is highly desirable to provide a mold release agent which improves the release characteristics without adversely affecting the surface coating characteristics of the resulting molded resin article. Additionally, it would also be highly desirable to provide an effective mold release agent which, as a secondary benefit, provides improved binding of coatings to the surface of the molded product.
It is a principal object of this invention to provide an improved process for the production of molded articles from polymeric resinous materials using a glycoside compound containing one or more fatty acid ester or ether groups as a mold release agent.
It is another object of this invention to provide improved moldable resin compositions which form molded articles that are easily removed from a mold and which have improved binding properties for coatings. Still further objects and advantages of this invention will be apparent by reference to the following description.
Throughout the specification and claims all ratios and percentages are stated on a weight basis, temperatures are in degrees Celsius and pressures are in KPascals over (or under) ambient unless otherwise indicated.